Preparation and characterization of adsorbents derived from bentonite and kaolin clays

The comparative study on preparation and characterization of modified bentonite and kaolin clay types is aimed at establishment of the ability of these clay types to adsorb pollutants. Its low cost, availability and recovery of clay give it added advantage of an effective adsorbent. The modified clay types were prepared by impregnation using various concentrations of either H2SO4 or NaOH in w/v ratio of 1:2. The physicochemical and adsorptive properties were investigated using standard physicochemical methods like moisture content, bulk density, pH, iodine and methylene blue numbers. FTIR, XRD and SEM analyses were also conducted on these clay types. Unmodified kaolin clay exhibited lowest moisture content (1.12%) while unmodified bentonite clay type had highest value (3.98%). The peaks at 3435 cm−1 and 3410 cm−1 assigned N–H stretching frequency were obtained for 2 M H2SO4 modified and unmodified bentonite clay types, respectively. The peaks at 912 cm−1 and 914 cm−1 that indicate the presence of Al–Al–OH deformation frequency were obtained for unmodified bentonite clay type and 2 M H2SO4 modified bentonite clay, respectively. The physical surface morphology of the clay types revealed the presence of pores with irregular shapes, while their XRD analysis showed that the clay types are crystalline. The modified clay types exhibited better potential adsorbent for removal of small metallic or gas molecules as well as large organic molecules. Adsorbents could also remove cations or anions of pollutants since their surface charge could be positive or negative depending upon pH condition.